BY-COVID - WP5 - Baseline Use Case: COVID-19 vaccine effectiveness assessment

Matching cases to controls (1:1) and assessing covariate balance after matching

A sequence of nested (daily) trials are emulated with increasing time (t1, t2, …, tn), iterating over the days in the enrollment period. At each eligible time during the enrollment period, the vaccination status of eligible individuals is assessed and every individual who has completed a primary vaccination schedule at that time (coded here as initiation of the intervention strategy when emulating a nested target trial) is matched to an individual who has not (yet) completed the primary vaccination schedule (coded here as the control strategy when emulating a nested target trial). Newly vaccinated individuals (completing a primary vaccination schedule) are eligible for inclusion in the study, even if they had previously been selected in the “no (or partial) vaccine group”. Vaccinations have been administered in the context of national public health programs, without interference/manipulation of the research subjects.

We assess the covariate balance, which is the extent to which the distribution of covariates is similar across the intervention groups.

Standardized Mean Differences

The Standardized Mean Difference (SMD) represents a standardized difference in mean between contrasted intervention groups for each covariate.

Means intervention group Means control group Standardized mean difference
distance 0.898848438 0.895000673 0.2045432558
sex_cd0 0.017416364 0.009977827 0.0568622458
sex_cd1 0.473374264 0.506651885 -0.0666498088
sex_cd2 0.509209372 0.483370288 0.0516869362
age_cd10 0.117027941 0.119733925 -0.0084179597
age_cd11 0.129933592 0.124168514 0.0171462146
age_cd12 0.127928831 0.143015521 -0.0451683046
age_cd13 0.111514848 0.096452328 0.0478526717
age_cd14 0.096604436 0.087583149 0.0305373248
age_cd15 0.068287182 0.073170732 -0.0193608748
age_cd16 0.044480642 0.046563193 -0.0101016068
age_cd17 0.026061897 0.017738359 0.0522443422
age_cd18 0.023180053 0.023281596 -0.0006748217
age_cd2 0.001754166 0.001108647 0.0154260491
age_cd3 0.002380654 0.000000000 0.0488501289
age_cd4 0.007267260 0.005543237 0.0202974469
age_cd5 0.013156246 0.011086475 0.0181648672
age_cd6 0.027064278 0.021064302 0.0369750888
age_cd7 0.044480642 0.042128603 0.0114087784
age_cd8 0.063400576 0.078713969 -0.0628416921
age_cd9 0.095476757 0.108647450 -0.0448177371
residence_area_cd731 0.155870192 0.146341463 0.0262693175
residence_area_cd732 0.149855908 0.154101996 -0.0118961317
residence_area_cd733 0.694273901 0.699556541 -0.0114661965
pregnancy_blTRUE 0.025435409 0.036585366 -0.0708187905
institutionalized_blTRUE 0.036837489 0.028824834 0.0425384506
foreign_blTRUE 0.148227039 0.137472284 0.0302673847
socecon_lvl_cd1 0.022678862 0.018847007 0.0257383002
socecon_lvl_cd2 0.137702042 0.118625277 0.0553612471
socecon_lvl_cd3 0.360481143 0.375831486 -0.0319705515
socecon_lvl_cd4 0.344067160 0.338137472 0.0124818939
socecon_lvl_cd5 0.135070793 0.148558758 -0.0394616672
comorbidities_blTRUE 0.501190327 0.483370288 0.0356401786
immunestatus_blTRUE 0.275654680 0.276053215 -0.0008918898
Means intervention group Means control group Standardized mean difference
distance 0.504282811 0.4957171893 0.166817773
sex_cd0 0.017532551 0.0090241073 0.064828877
sex_cd1 0.472218641 0.4964548150 -0.048547344
sex_cd2 0.510248808 0.4945210777 0.031462070
age_cd10 0.116668815 0.1303338920 -0.042566986
age_cd11 0.130978471 0.1387134201 -0.022926736
age_cd12 0.127884491 0.1361351038 -0.024705306
age_cd13 0.111512183 0.1125435091 -0.003276493
age_cd14 0.095784453 0.0960422844 -0.000876098
age_cd15 0.068067552 0.0666494779 0.005630366
age_cd16 0.044862705 0.0417687250 0.014946580
age_cd17 0.025654248 0.0197241201 0.037508340
age_cd18 0.023075931 0.0193373727 0.024899704
age_cd2 0.001804821 0.0005156633 0.030372557
age_cd3 0.002449401 0.0012891582 0.023472068
age_cd4 0.007219286 0.0043831378 0.033500794
age_cd5 0.013149413 0.0092819389 0.033950687
age_cd6 0.027201238 0.0212711100 0.036455092
age_cd7 0.044347041 0.0407373985 0.017534033
age_cd8 0.063684414 0.0643289932 -0.002639663
age_cd9 0.095655537 0.0969446951 -0.004383129
residence_area_cd731 0.156117056 0.1486399381 0.020600033
residence_area_cd732 0.150058012 0.1459327059 0.011551329
residence_area_cd733 0.693824932 0.7054273559 -0.025173225
pregnancy_blTRUE 0.025009669 0.0192084569 0.037150494
institutionalized_blTRUE 0.037643419 0.0313265438 0.033188662
foreign_blTRUE 0.148768854 0.1414206523 0.020649108
socecon_lvl_cd1 0.022560268 0.0105710971 0.080736893
socecon_lvl_cd2 0.137811009 0.1336857032 0.011967763
socecon_lvl_cd3 0.359804048 0.3765631043 -0.034918862
socecon_lvl_cd4 0.345752224 0.3560654892 -0.021684159
socecon_lvl_cd5 0.134072451 0.1231146062 0.032159892
comorbidities_blTRUE 0.501095784 0.5016114477 -0.001031329
immunestatus_blTRUE 0.277684672 0.2776846719 0.000000000

Propensity score distribution